Responses of soil microbial metabolic limitations to erosion under contrasting soil types and management practices

Abstract

AbstractSoil microbial metabolism plays an important role in supporting soil services and functionalities but is usually restricted by the availability of soil nutrients. Although soil microbial metabolism limitation (SMML) has been widely addressed with regard to various driving factors, its response to erosion has not been examined but is urgently needed given the important influence of erosion on global environments. To understand how erosion affects SMML and whether erosion's effect varies with tillage practices and soil types, we conducted a simulated erosion experiment to compare eroded and noneroded plots with contrasting soil types (Mollisol vs. loess soils) and managements (conventional tillage versus no‐tillage in plots with crops versus without crops). We measured soil extracellular enzymatic activities and quantified SMML with extracellular enzymatic stoichiometry models. In both soils, the microbes were limited by carbon (C) and phosphorus (P), but not by nitrogen, and microbial C and P limitations were greater in Mollisol than loess soils. For the Mollisol, erosion significantly increased the relative C limitation, whereas the presence of crops eliminated this increase. For the loess soils, erosion enhanced the relative C limitation regardless of crop presence and tillage management. Erosion consistently increased microbial P limitation in plots with crops, with greater effects under no‐tillage (+2.9%) compared to conventional tillage (+0.7%) conditions regardless of soil type (p < 0.05). In plots without crops, microbial P limitation was increased by erosion under no‐tillage (+2.1%) but was decreased under conventional tillage (−5.6%) (p < 0.05). Additionally, conventional tillage exacerbated microbial C limitation but alleviated microbial P limitation. These results indicated that erosion shifted microbial C and P limitations depending on soil type, tillage practice and the presence of plants, highlighting the importance of considering all these factors when assessing soil microbial metabolic limitation at various spatial scales.